Circuits including a flip-flop and a delay for generating two pulses



April 5, 1966 ANATOLE TURECKl 3,244,985

CIRCUITS INCLUDING A FLIP-FLOP AND A DELAY FOR GENERATING TWO PULSES Filed OCI'.. 3l, 1965 A I 5 f I ,f//-/za A :c

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l f a/5 IW- L75 I NVE N TOR. 4A/47m# 75475K/ United States Patent O 3,244,985 CIRCUITS INCLUDING A FLIP-FLOP AND A DELAY FOR GENERATIN G TWO PULSES Anatole Tureck, North Palm Beach, Fla., assignor to Radio Corporation of America, a corporation of Dela- Ware Filed Oct. 31, 1963, Ser. No. 320,412 7 Claims. (Ci. 328-74) This invention relates to new and improved circuits for generating two consecutive timing pulses. Such circuits are commonly used in input-output control modules of data processing machines.

The circuits of the invention include a flip-flop, a feedback path from one of the output terminals of the flipop to one of the input terminals of the flip-flop, and a delay means in the feedback path. The feedback path may also include, in a specific form of the invention, a multiple input coincidence gate, such as a NOR gate. The output pulses are taken from the input and output terminals, respectively, of the delay means.

The invention is discussed in greater detail below and is shown in the following drawings of which:

FIGS. la-lc are drawings of symbols employed in FIGS. 2 and 3;

FIGS. 2 and 3 are block circuit diagrams of two different forms of the invention; and

FIGS. 4 and 5 are drawings of waveforms which are referred to in the explanation .of the operation of the circuits of FIGS. 2 and 3, respectively.

FIGS. la-lc are believed to be self-explanatory. The truth table to the right of the flip-flop lin FIG. la gives the convention assumed for the ip-op. Ther Boolean equation to the right of the NOR ga-te of FIG. 1b denes the logic operation performed by this gate. The delay means of FIG. lc may comprise a delay line. Al-so, it may be desirable to include in the delay means driver and receiver transistors, at the input and output ends respectively of the delay line, for improving the wave shape and amplitude.

The circuit of FIG. 2 includes a NOR gate 10 which is connected through a delay means 12 to the set (S) terminal of flip-flop 14. The X output of the flip-flop is fed back as one of the inputs to NOR gate 10. The output terminal of delay means 12 is connected as a second input to NOR gate 1t) via lead 16. The third input to the NOR gate is input signal A which is applied to terminal 18. The signal is also applied via lead 20 to the reset (R) terminal of flip-flop 14. l

In the discussion which follows of the operation of the circuit of FIG. 2, both FIGS. 2 and 4 should be referred to. Also, in this explanation, the assumption is arbitrarily made that a relatively high level signal represents the binary digit one and a relatively low level signal represents the binary digit zero. For the sake of brevity,

the outputs and inputs to various circuits are referred to as ones or zeros ratherthan as signals representing ones or zeros.

Initially, A, the input signal, is a one causing p-op 14 to be reset. lIn this condition X :0. X :0 is a` priming signal for NOR gate 10. TP-2 is also initially zero and this also acts as a priming signal for NOR gate 10.

When A changes from one to zero, the three inputs to NOR gate 10 are all zero and the NOR gate therefore becomes enabled. Accordingly, TP-l changes from zero 3,244,985 Patented Apr. 5, 1966 to one. After the interval At inserted by delay means 12, TP-Z change-s from zero to one. This sets ip-op 14 changing X to one. When X changes to one, NOR gate 10 becomes disabled so that TP-l changes back to zero. The time required after the occurrence of the signal A=0, for X tol change from zero to one, is substantially equal to the delay interval At inserted by the delay means 12. Therefore, the duration of timing pulses TP-l is also equal to' At.

At the time TP-l changes to zero, TP-2 is still a one. However, after the delay interval At, the zero arrives at the output of delay means 12 so that TPeZ changes to zero. Thus, the duration of pulse TP-Z, as well as of pulse TP-l, is also At.

An important feature of the circuit of FIG. 2 is that it is insensitive to the duration of the A=0 pulse. If the A=0 pulse is equal to or longer than At, as illustrated in FIG. 4, then thetwo output pulses each have a duration At and the leading edge of the second output pulse is coincident with the lagging edge of the first output pulse. If the duration of the A=O pulse is less than A,t,` the two output pulses each have the duration of the A=0 pulse, and the leading edge of the second output pulse is spaced from the lagging edge of the first output pulse. Another feature of the circuit of FIG. 2 is that it is self-resetting.

The circuit of FIG. 3 includes a llip-op 22 and a delay means 24. The X output terminal of the flip-flop is connected through the delay means 24 to the reset terminal of the flip-flop 22.

In the discussion which follows of the operation of the circuitof FIG. 3, `both FIGS. 3 and 5 should be referred to. It is assumed that the flip-'op is initially-reset so that X :0. -When the input signal A is changed to a one, this sets the flip-flop yand TP-1 changes from zero to one. After the interval Atl-inserted by delay line 24, rl`P-2 changes to one and this resets flip-dop 22. When the flip-flop 22 is reset, X changes'to zerol so that. TtP-l changes back to zero. After the interval Atl, timing pulse TP-Z changes back to zero. Both timing pulses TP-l and TP-2 therefore have the vsame duration, namely a duration substantially equal to Atl. 'Y

The circuit of FIG. 3 is somewhat simpler than the one of FIG. 2 since the NOR gate is not required. Howeven in the circuit of FIG. 3 the input pulse A must be not greater than Atl, the delay inserted by the delay means. In certain data processing circuit applications where an input command pulse is relatively short, the circuit of FIG. 3 may be employed. In others, where relatively long direct current levels are employed to actuate the pulse generator, the circuit of FIG. 2 is used.

In the circuit of FIG. 2 a NOR gate is employed as the input coincidence gate. It should be appreciated that other types of coincidence gates may be employed instead. As one example, with minor circuit modification, an AND gate may be substituted for the NOR gate. In this event, the rather than the X output terminal is connected back to the coincidence gate. Also, inverters are inserted in series with the leads 16 and 20. Also, the actuating signal is 1 .1 rathen'than A=0. g In the circuit of FIG. 3 a set-reset flip-flop is employed. A triggerable ilip-liop may beused instead. In this case the triggering pulse A may be applied tothe trigger input terminal. In a particular triggerable flip-flop in practical use as a data processing machine module, an A=1 pulse 3. applied to the trigger input terminal does not prevent a 1 on the set or 'reset' terminalV from setting or resetting the flip-flop, respectively. Therefore, when this triggerable flip-flop is used in the circuit of FIG. 3, the A=1 pulse can have any duration, including a duration substantially greater than Atl.

In both the circuits of FIGS. 2 and 3 the minimum duration of the A pulse is not given. In both cases the minimum duration of the A pulse is that duration requiredto change the state of a flip-flop.

In the` circuit ofV FIG. 3, employing a triggerable ilipflop, it ispossible to generate relatively l'ong output pulses evenif multiple inputipulsesare present duri-ng. the period of TP'2`.' For example, assume that each suchinput pulse -has a duration of Ata and that there are ve such input pulses spacedL intervals Stg during TP-2`. Assume also that the delay line duration is At?, which is say twelve times the duration of Atz. In a circuit of this type, the output pulses TP-l and TP-Z produced will each have' the duration Ata and will be unaffected. by the fact that multiple inputY pulses-are occurring during the time TP-Z is produced.

It is possible to operate the circuit of FIG. 3 in still another way if the hip-hop is of the' type which is capableA of. assuming' three states. Two ofthe states are` shown in FIG. laf.. The third state is` that in which ai one present at both. set and reset input terminals produces a zero at both the X and output terminals, If a iiip-tlop of this type is employed, the A pulse applied' to the set terminal of FIG. 3 may have a duration of' less than or more than.. 2At`1 and, in either case, two output pulses TP-land TP Z', each of duration Atl are produced.

What is claimed is:

1-. A two pulse generator circuit comprising', in" combination:

a flip-flop having two input terminals;

means coupled.v to one input' terminal of the flip-flop` for' switching the Hip-flop from' a. rst" to aA second storage state;

a circuit', including' delay' means, directly connected between an. output terminal and a second input' terminal of vthe nip-flop forl switching the nip-nop back t-'o' its rs't' storage' state",Y after the delay interval inserted" by the delay means, in' response to the output signal produced' by' the' ilipilop; when it is switched from its first to it's second storage state;

an output" terminal at the input'terminal' ofthe delay means at which one output pulse isV produced; and

an output terminal at the output terminal to" the delay means at which a second output pulse' is produced;

2. In combination:

la coincidence gatehaving three4 inputy terminals;

a tlip-tlop'" having two input terminals;

a delay means" connectedv a-t its input terminal to the output terminal of the gate and connected: at its output'y terminal to`- the' first of thev input terminals to the flip-Hop and to one of the input terminals to the the gate, for placingV the ip-flp in a first state and disabling the gate in response toa signal indicative of a4 binary digit o'f one value and for tending toenable the" gate iny response to' a' signal indicative of a binary digit of the' other value;

means coupled toi a second? input terminalv of the' gate and t'olthe: second: input terminalo't theV ilip-ii'op1 for disabling the. gate" and. placing-f the ilip-flopinits secondstate inV response toasignal indicative of a binary digit ofone value, and for tending: to enable the gate in response to a signal. indicative of a binary digit of the other value; andr a feedbackconnectionirom an output terminalof. the flip-hop to the third input terminal of the gate for applying a signal to the gate which tendsto enable the gate when said flip-flop is, in said second'r state', and which disables the gate when 'saidflip-iio'p is in itstirststate. i i' 3. In combination:

a coincidence gate having three input terminals;

a flip-flop having two input terminals;

a delay means connected at its input terminal to the output terminal of the gate and connected at its output terminal to the rst of the input terminals to the flip-flop and to one of the input terminals to the gate, for placing the flip-flop in a rst state and disabling the gate in response to a signal indicative of a binary digit of one value and for tending to enable the gate in responseto a signal indicative of a binary digiti of the vother value;

means coupledv to a second input terminal of the gate and to the second' input terminalv of the flip-hop for disabling the gatey and placing the flip-hop in its second state in response to a signal indicative of a binary digit of one value; and for tending to enable the gate in responsev t'o aA signal indicative of a binary digit of the other value;

a feedback connection from an output terminal of the hip-nop to the third input terminal of the gate for applying a signal to the gate which tends to enable the gate when said flip-flop i's in said second state, and which disables thev gate when said flip-flop is in its irst state;

an output terminalv at the input terminal of the delay meansV at' which one output pulse is produced; and

an output terminal at the output terminal to the delay means at which a secondoutput pulse is produced'.

4. Incombination:

a NOR gate havingthreeinputr terminals;

a flip-ophaving two input terminals;

a delay means connected at its' input terminal to' the output terminal of the gate andconnected at its output terminal to the rst of the input terminals to the Hip-HopV and' to one' of the' input terminals to the gate, for placing the ipfl'op in al first state in' response toa signal indicative of the binary digit one and for tending to enable the gate in response to a signal indicative ofthe binary digit Zero;

means coupled' to" asecond' inputv terminal of the gate and' to the" second input terminal of the flip-flop for disabling the` gate and placing the ilip-'op in its secondt statein respon'seto a signal indicative of the binary digit one, and fortending to enable the gate in `response to a signalj indicative of the binary digit zero; andVj a'Y feedback connection from anv output terminal of the tlipliiop to the third input terminal' of the gate for' applying a signal to the gate which tendsto enable the gate when said tlip-op isfin said second state, and which disables thel gate when said flip-o'p is in-its first state.

5. A circuit1 for' generating twov pulses of the same durationc'omprisrlg, in combination a delay me'ans'having'an input terminal and an output terminal;

means'Y for applying an input direct current level to the input terminal of the delay means -of a duration longer than the delay introduce'dby the delay means;

a feedback path fromi the outputterminal of the delay means to the input terminalftliereot for unconditionally inhibiting'Y the input' to` the` delay means in response to"A the delayed direct current level which appears at the output' terminal of the delay means;

andi two -output terminals, one at the input terminal of-A the'.l delay.I means and onef at the output terminal of the delay means at which two output pulses of the same duration arefprodu'ced.

6'. A two" pulseV generator circuit comprising, in combinati'om a flip-flop havingv rstI and second'input' terminals and an output terminal;

means for applying a signal to the iirst input terminal for changingY the stateof the Hip-flop;

a feedback path between said output terminal and the 7. A two pulse generator circuit as set forth in claim second input terminal of said Hip-tlop for applying 6 wherein said feedback path consists solely of said delay a signal to said second terminal for restoring the mearm lip-op responsive to said change of state of said References Cited by the Examiner fli `o to its original storage state, said feedback parth inlcluding a delay means; 5 UNITED STATES PATENTS an output terminal at the input terminal of said delay 2,892,998 6/ 1959 Eckert et al. 328-55 means at which one output pulse is produced; and 3,1475342 8/ 1964 Hill 307-885 an output terminal at the output terminal of the delay means at which a second output pulse is produced. 10 ARTHUR GAUSS, Primary Examiner. 

1. A TWO PULSE GENERATOR CIRCUIT COMPRISING, IN COMBINATION: A FLIP-FLOP HAVING TWO INPUT TERMINALS; MEANS COUPLED TO ONE INPUT TERMINAL OF THE FLIP-FLOP FOR SWITCHING THE FLIP-FLOP FROM A FIRST TO A SECOND STORAGE STATE; A CIRCUIT, INCLUDING DELAY MEANS, DIRECTLY CONNECTED BETWEEN AN OUTPUT TERMINAL AND A SECOND INPUT TERMINAL OF THE FLIP-FLOP FOR SWITCHING THE FLIP-FLOP BACK TO ITS FIRST STORAGE STATE, AFTER THE DELAY INTERVAL INSERTED BY THE DELAY MEANS, IN RESPONSE TO THE OUTPUT SIGNAL PRODUCED BY THE FLIP-FLOP, WHEN IT IS SWITCHED FROM ITS FIRST TO ITS SECOND STORAGE STATE; AN OUTPUT TERMINAL AT THE INPUT TERMINAL OF THE DELAY MEANS AT WHICH ONE OUTPUT PULSE IS PRODUCED; AND AN OUTPUT TERMINAL AT THE OUTPUT TERMINAL TO THE DELAY MEANS AT WHICH A SECOND OUTPUT PULSE IS PRODUCED. 